Thermal conversion of hydrocarbons



Patented Jan. 25, 1 949 THERMAL CONVERSION .OF HYDROCARBONS Carlisle M. Thacker, "Highland Park, and Hillis 0. Folkins, -Skokie,-Ill., assignorsito-The Pure Oil Company, Chicago, 111., acorporation of Ohio .No Drawing. Application Novemher18, 1944, SerialNo. 564,180

1 Claim. (Cl. 196-52) This invention relatesto the conversion of hydrocarbons and is particularly directedto cracking of hydrocarbons in the presence "of a small amountof an explosive substance. This application is a continuation-in-part of our co-peuding applicationSerial No. 434,790 filed March 14, 1942 now-Patent No. 2,435,760 entitled Thermal conversion of hydrocarbons.

We have discovered thatif hydrocarbons are subjected to suitable time, temperature and pressure conditions to crack the hydrocarbons, in the presence of a small amount-of an explosive substance, the cracking reaction is promoted so that hi'gher yields of cracked products can be obtained and cracking can be effected at lower temperatures. Although it is not known why explosive substances promote the cracking reaction, it is thought the shock of or the energy produced in the decomposition of the explosive is communicated to the intimately associated hydrocarbon molecules undergoing decomposition, thus facilitating scission of the carbon to carbon bonds.

One-oi the objects of the invention is to pro vide an improved method of converting higher boiling hydrocarbons into lower boiling hydrocarbons.

vAnother object of the invention is to accelerate the rate of cracking in thermal cracking operations.

Qther objects of the invention will become manifest from the following description.

In accordance with the invention, hydrocarbons to be converted are subjected to conversion conditions of time, temperature and pressure in admixture with a small amount of an explosive substance which explodes when heated to or below the temperature of the cracking reaction. The explosive substance is preferably injected directly into the reaction zone in the form of a solution in a solvent; or where hydrocarbon liquid is cracked, in solution or suspension in a portion of the hydrocarbon liquid to be cracked. It is important that the explosive substance shall not be subjected to such temperatures prior to the time it enters the reactor as to cause decomposition thereof. Explosive substances may be injected into the reaction zone in an amount of approximately .05 to 3 mol percent of the hydrocarbons undergoing cracking, depending upon the particular compound used.

Any known explosive compound whether organic or inorganic which is capable of explodin under reaction conditions may be used. As exampl-es "of endothermic compounds which are useful, the following are given:

Organic nitro compounds l, i6-trinitroaniline (T. 'N. Y A, picramide) 6;, G-trinitrocresol 3, l-trinitrotol uene ,="6-trinitrotoluene '(T. N. 'T.)

. rinitrephenylmethylnitramine (tetryl) icric acid 3, i, 6 tetranitrophenol Nitrocellulose Nitrog'lycerin Nitromannite Benz-azide Chrysammic acid Glycol 'dinitrate Dinitromethane Benzylazide Lead salt of trinitroresorcinol Nitrosoguanidine Nitro'urea Trinitroethanenitrile to IT; 3 50 Ammonium compounds a halogen or a hydrohalide, particularly bromine,

iodine, hydrogen iodide or hydrogen bromide, are particularly effective since these halogens and hydrohalides in themselves are very effective cracking sensitizers. Compounds which decompose to form a free oxygen atom are also highly effective, since free oxygen in itself has a sensitizing efifect on the cracking reaction. Metal salts, particularly mercury salts, are also good 3 sensitizers since mercury is an active cracking catalyst.

Cracking in the presence of explosive substances may be carried out under sub-atmospheric, atmospheric or super-atmospheric pressures and at temperatures ranging from the lowest temperature at which cracking will occur to a temperature of approximately 2000 F., depending upon the nature of the charging stock and the type of product it is desired to produce. When cracking of hydrocarbon oil is conducted for the purpose of making lower boiling hydrocarbon liquid, such as gasoline, temperatures ranging from approximately 650 to 1200 F. may be used. Where cracking of hydrocarbon oils or gases for the purpose of aromatic hydrocarbons is practiced, temperatures of approximately 1000 to 1500. F. may be used. If it is desired to produce butadiene from hydrocarbon oils, temperatures in the Vicinity of 1300 to 1600 F. give the best yields and where it is desired to crack hydrocarbon oils to gaseous hydrocarbons, temperatures from approximately 1300 to 2000 F. may be used.

The invention is adapted for use in conjunction with conventional types of purely thermal as well as catalytic cracking operations without the necessity of changing the operation of said process or the apparatus required except to make provision for charging the explosive substance to the reaction zone.

As an example illustrating how the invention may be practiced, gas oil is charged to a preheating coil in a thermal cracking operation conducted at a maximum temperature of approximately 900 F. and at a pressure of approximately 500 pounds per square inch. In the pre-heatm coil, the gas oil is heated to a temperature of approximately 700 F., and passes into the cracking coil into which a solution of trinitrotoluene in a portion of the gas oil is injected in such amounts that the moi ratio of trinitrotoluene to gas oil undergoing cracking is .001 to 1. The trinitrotoluene solution is injected into the inlet of reaction coil. The yield of gasoline obtained is considerably in excess of that which is obtained in a similar operation without using any cracking sensitizer.

As another example, a solution of benzoyl peroxide in benzene is injected into a cracking zone in which gas oil is undergoing cracking at a temperature of approximately 850 F. The moi ratio of benzoyl peroxide to gas oil is approximately .01 to 1. The yield of gasoline is as good as can be obtained at higher temperatures Without sensitizers.

Although the specific examples are directed to cracking of gas oil, it is to be understood that the invention is applicable to cracking of methane to acetylene, cracking of propane and butanes to ethylene and propylene and cracking of hydrocarbon oils in general to lower boiling hydrocarbons.

It will be seen, therefore, that we have succeeded in improving hydrocarbon cracking processes in that by adding a small amount of explosive to the hydrocarbon undergoing cracking, yields of desirable products can be materially increased for any particular set of reaction conditions or the reaction can be carried out at lower temperatures and/or in less time without suffering any decrease in yield of desirable products.

We claim:

The process of cracking hydrocarbon oils to hydrocarbons within the gasoline boiling range comprising, subjecting said oils to temperatures of approximately 650 to 1200 F., in a cracking zone in the presence of about 0.05 to 3.0 mol per cent of ethyl hypochlorite.

CARLISLE M. THACKER, HILLIS O. FOLKINS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 237,662 De Smedt Feb. 8, 1881 1,673,496 Churchill June 12, 1928 1,898,966 Spilker Feb. 21, 1933 2,007,226 Szayna July 9, 1935 2,012,959 Colony Sept. 3, 1935 2,259,630 Frey Oct. 21, 1941 2,329,896 Harsch Sept. 21, 1943 OTHER REFERENCES Sickman et al., Journal of Chemical Physics, vol. 4, pages 608-613, September 1936.

Heilbron, Dictionary of Organic Compounds," vol. I, pages 204 (1943). 

